Thumbnail generating apparatus and image shooting apparatus

ABSTRACT

Based on, for example, the image at the start of a movie, a thumbnail image is tentatively generated and is stored in a header file. If a predetermined triggering condition is fulfilled during movie shooting, a thumbnail image is generated from the frame image at the timing that the triggering condition is fulfilled, and the thumbnail image existing in the header file is replaced with the newly generated thumbnail image. The triggering condition is fulfilled, for example, if, after zooming-in, the angle of view has been kept fixed for a predetermined period or longer, or if the focus has been kept locked for a predetermined period.

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2006-084882 filed in Japan on Mar. 27, 2006and Patent Application No. 2006-084967 filed in Japan on Mar. 27, 2006,the entire contents of both of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thumbnail generating apparatus foruse in an image shooting apparatus such as a digital still camera ordigital video camera. The invention also relates to an image shootingapparatus incorporating such a thumbnail generating apparatus.

2. Description of Related Art

Image shooting apparatuses such as digital video cameras typically havea mode in which they display thumbnail images. Thumbnail images ofmovies are generated at appropriate timing, for example at the start orend of their recording (hereinafter this method of thumbnail generationwill be called conventional method 1). Image shooting apparatuses ofthis type are disclosed in, for example, JP-A-H10-028250,JP-A-2001-111963, JP-A-2005-229236, and JP-A-H8-251540. While viewingthose thumbnail images, the user can select from a plurality of recordedmovies the one he wants to play back. FIG. 14 is a flow chart showingthe conventional method of thumbnail generation.

According to another conventionally proposed method (hereinafter calledconventional method 2), at the end of recording of a movie (movingpicture), the user is allowed to check through the movie to search for aframe of which the image he wants to select as a thumbnail image.

According to yet another conventionally proposed method (hereinaftercalled conventional method 3), an image shooting apparatus is providedwith a switch dedicated for thumbnail generation so that, whenever it ispressed, a thumbnail image is generated from the image of the frame atthat timing (see, e.g., JP-A-2002-077803)

On the other hand, there have also been proposed image shootingapparatuses capable of shooting still images while shooting a movie.This type of image shooting apparatus is typically capable of shootingand recording high-resolution still images while shooting a movie. Thiscapability meets the demands of people who want, for example, to shootthe whole event of their kids running a race on a field day andmeanwhile record the scenes at crucial moments, such as the runnersreaching the finish line, in high-resolution still images.

If the user can make thumbnail images from impressive images, he caneasily select among movies for playback. Inconveniently, however, with amethod like conventional method 1 whereby thumbnail images are generatedat appropriate timing, the thumbnail images often do not aptly representthe shot movies. This often makes it difficult to efficiently select thedesired movie based on the thumbnail images.

Conventional method 2 imposes extra operation on the user. Conventionalmethod 3 likewise imposes on the user extra operation of pressing thededicated switch in the middle of recording, and in addition requiresthe provision of the dedicated switch.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a thumbnailgenerating apparatus has the following features: based on a sensed-imagesignal representing a subject received from an image shooting portionprovided in an image shooting apparatus capable of shooting a movie, thethumbnail generating apparatus generates a thumbnail image associatedwith the shot movie; the thumbnail generating apparatus includes a firstgeneration portion generating, based on the sensed-image signal atprescribed timing, a first candidate thumbnail image as a candidate forthe thumbnail image; and, when a predetermined triggering condition isfulfilled during shooting of the movie, based on the sensed-image signalat predetermined timing relative to when the triggering condition isfulfilled, the thumbnail generating apparatus generates a secondcandidate thumbnail image different from the first candidate thumbnailimage and associates, as the thumbnail image, the second candidatethumbnail image with the movie.

Specifically, for example, the image shooting apparatus may include aview angle changing portion that allows the angle of view at which theimage shooting portion performs shooting to be changed, and thetriggering condition may include a condition that, after zooming-in isperformed to decrease the angle of view, no change has been made in theangle of view by the view angle changing portion for a predeterminedperiod or longer.

Specifically, for another example, the image shooting apparatus mayinclude an autofocus control portion that automatically adjusts theposition of the focus lens so that an optical image representing thesubject is focused on the image sensing surface of an image sensingdevice, and the triggering condition may include a condition that thewidth of variation of the position has remained smaller than or equal toa predetermined threshold value for a predetermined period or longer.

Specifically, for another example, the image shooting apparatus mayinclude a motion detecting portion that detects motion within a motiondetection area in an image based on the sensed-image signal, the motiondetection area being defined in a shot image included in the movie, andthe triggering condition may include a condition that the magnitude ofthe detected motion has remained smaller than or equal to apredetermined threshold value for a predetermined period or longer.

Specifically, for another example, the image shooting apparatus mayinclude a face area detection portion that detects a person's face areain a shot image included in the movie based on the sensed-image signal,and the triggering condition may include a condition that the size ofthe detected face area is larger than or equal to a predeterminedthreshold value.

Specifically, for another example, the image shooting apparatus mayinclude a sound input portion that receives input of sound from theoutside so that whether or not the triggering condition is fulfilled ischecked based on the intensity or loudness of the sound inputted duringshooting of the movie, and the second candidate thumbnail image may begenerated from the sensed-image signal at predetermined timing relativeto when the intensity or loudness of the sound, or the intensity orloudness of the frequency component of the sound in a predeterminedband, is maximal during shooting of the movie.

Specifically, for another example, when the triggering condition isfulfilled during shooting of the movie, the second candidate thumbnailimage may be generated from the sensed-image signal at the frame duringwhich the triggering condition is fulfilled or at a frame close to thatframe.

“A frame close to that frame” is, for example, the frame several framesbefore or after the frame during which the triggering condition isfulfilled; it may even be, for example, the frame several tens of framesbefore or after the frame during which the triggering condition isfulfilled.

Specifically, for another example, when the triggering condition is notfulfilled even once during shooting of the movie, the first candidatethumbnail image may be associated, as the thumbnail image, with themovie.

Specifically, for another example, the image shooting apparatus may becapable of shooting a still image during shooting of the movie, and thetriggering condition may include a condition that an instruction toshoot the still image is entered.

According to a second aspect of the present invention, an image shootingapparatus capable of shooting a movie includes the image shootingportion mentioned above and the thumbnail generating apparatus accordingto the first aspect of the invention described above.

According to a third aspect of the present invention, a thumbnailgenerating apparatus has the following features: based on a sensed-imagesignal representing a subject received from an image shooting portionprovided in an image shooting apparatus capable of shooting a stillimage during shooting of a movie, the thumbnail generating apparatusgenerates a thumbnail image associated with the shot movie; and, when astill image is shot during shooting of the movie, the thumbnailgenerating apparatus generates the thumbnail image from the sensed-imagesignal at predetermined timing relative to when the still image is shot.

Specifically, for example, the thumbnail image may be generated from thesensed-image signal representing the still image.

Specifically, for another example, the thumbnail generating apparatusmay include a selection portion that, when a plurality of still imagesare shot during shooting of the movie, selects one of the still imagesas an adopted still image, and the thumbnail image may be generated fromthe sensed-image signal at predetermined timing relative to when theadopted still image is shot.

Specifically, for another example, which of the still images to selectas the adopted still image may be prescribed.

Specifically, for another example, the thumbnail generating apparatusmay include a contrast detection portion that defines a predeterminedcontrast detection area in each of the still images and that, based onthe sensed-image signal representing the shot still images, detects thedegree of contrast within the contrast detection area for each of thestill images, and the selection portion may select the adopted stillimage based on the results of the comparison of the degree of contrastamong the still images.

Specifically, for another example, the thumbnail generating apparatusmay include an area division portion that defines a predetermineddetection area in each of the still images and that, based on thesensed-image signal representing the shot still images, divides, in eachof the still images, the detection area into a plurality of brightnessregions or a plurality of color regions, and the selection portion mayidentify, in each of the still images, a brightness region or colorregion having the largest area among all the brightness regions or colorregions, and select the adopted still image based on the results of thecomparison of the area of the brightness region or color region havingthe largest area among the still images.

Specifically, for another example, the image shooting apparatus mayinclude a sound input portion that receives input of sound from theoutside, and the thumbnail generating apparatus may include a sounddetection portion that detects, for each of the shot still images, theintensity or loudness of the sound, or intensity or loudness of thefrequency component of the sound in a predetermined band, correspondingto the timing that the still image is shot so that the selection portionselects the adopted still image based on the results of the comparisonof the intensity or loudness of the sound or the intensity or loudnessof the frequency component of the sound in the predetermined band amongthe still images.

Specifically, for another example, when a plurality of still images areshot during shooting of the movie, part or all of the still images maybe selected as adopted still images so that there are a plurality ofadopted still images, and, for each of the adopted still images, athumbnail element image may be generated from the sensed-image signal atpredetermined timing relative to when the adopted still image is shot sothat the thumbnail image is generated by synthesizing together thumbnailelement images of the adopted still images.

According to a fourth aspect of the present invention, an image shootingapparatus capable of shooting a still image during shooting of a movieincludes the image shooting portion mentioned above and the thumbnailgenerating apparatus according to the third aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall block diagram of an image shooting apparatusaccording to a first embodiment of the invention;

FIG. 2 is an internal block diagram of the image shooting portion shownin FIG. 1;

FIG. 3 is an internal block diagram of the video signal processingportion shown in FIG. 1;

FIG. 4 is an internal block diagram of the AF value detection portionshown in FIG. 3;

FIG. 5 is a diagram showing an example of the screen displayed on thedisplay portion shown in FIG. 1 in a thumbnail image display mode;

FIG. 6 is a diagram showing the screen for playing back a movie, towhich screen the screen shown in FIG. 5 can be switched;

FIG. 7 is a flow chart showing the procedure for generating a moviethumbnail in the image shooting apparatus shown in FIG. 1;

FIG. 8 is a table listing examples of the triggering condition in stepS11 shown in FIG. 7;

FIG. 9 is a diagram illustrating a first check method for checkingwhether or not the triggering condition is fulfilled in step S11 shownin FIG. 7;

FIG. 10 is a diagram illustrating a second check method for checkingwhether or not the triggering condition is fulfilled in step S11 shownin FIG. 7;

FIG. 11 is a diagram illustrating a third check method for checkingwhether or not the triggering condition is fulfilled in step S11 shownin FIG. 7;

FIG. 12 is a diagram illustrating a third check method for checkingwhether or not the triggering condition is fulfilled in step S11 shownin FIG. 7;

FIG. 13 is a diagram illustrating a fifth check method for checkingwhether or not the triggering condition is fulfilled in step S11 shownin FIG. 7;

FIG. 14 is a flow chart showing the procedure for generating a moviethumbnail in a conventional image shooting apparatus;

FIG. 15 is an overall block diagram of an image shooting apparatusaccording to a second embodiment of the invention;

FIG. 16 is an internal block diagram of the video signal processingportion shown in FIG. 15;

FIG. 17 is a flow chart showing the procedure for generating a moviethumbnail according to a first generation method in the secondembodiment;

FIG. 18 is a flow chart showing the procedure for generating a moviethumbnail according to a second generation method in the secondembodiment;

FIG. 19 is a diagram illustrating a second selection method applied tothe second generation method in the second embodiment;

FIG. 20 is a diagram illustrating the second selection method applied tothe second generation method in the second embodiment;

FIG. 21 is a diagram illustrating a third selection method applied tothe second generation method in the second embodiment;

FIG. 22 is a flow chart illustrating the third selection method appliedto the second generation method in the second embodiment;

FIG. 23 is a diagram illustrating the third selection method applied tothe second generation method in the second embodiment;

FIGS. 24A and 24B are diagrams illustrating the third selection methodapplied to the second generation method in the second embodiment;

FIG. 25 is a flow chart showing the procedure for generating a moviethumbnail according to the third generation method in the secondembodiment; and

FIG. 26 is a diagram showing an example of a synthesized thumbnail imageof a movie according to the third generation method in the secondembodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the invention will be described by way ofspecific examples with reference to the accompanying drawings. In thesedrawings, the same parts that appear in more than one of them areidentified with the same reference numerals.

First Embodiment

First, a first embodiment of the invention will be described. FIG. 1 isan overall block diagram of an image shooting apparatus 1 according tothe first embodiment of the invention. The image shooting apparatus 1 iscapable of shooting movies and still images, and is even capable ofsimultaneously shooting still images while shooting a movie

The image shooting apparatus 1 includes an image shooting portion 11, anAFE (analog front end) 12, a video signal processing portion 13, amicrophone (sound input portion) 14, an audio signal processing portion15, a compression portion 16, an SDRAM (synchronous dynamicrandom-access memory) 17 as an example of an internal memory, a memorycard 18, a decompression portion 19, an image output circuit (videooutput circuit) 20, a sound output circuit 21, a TG (timing generator)22, a CPU (central processing unit) 23, a bus 24, a bus 25, an operatedportion 26, a display portion 27, and a loudspeaker 28. The operatedportion 26 includes a record button 26 a, a shutter button 26 b,operation keys 26 c, etc.

Connected to the bus 24 are the image shooting portion 11, the AFE 12,the video signal processing portion 13, the audio signal processingportion 15, the compression portion 16, the decompression portion 19,the image output circuit 20, the sound output circuit 21, and the CPU23. These blocks connected to the bus 24 exchange various signals (data)with one another via the bus 24.

Connected to the bus 25 are the video signal processing portion 13, theaudio signal processing portion 15, the compression portion 16, thedecompression portion 19, and the SDRAM 17. These blocks connected tothe bus 25 exchange various signals (data) with one another via the bus25.

The TG 22 generates timing control signals for controlling the timing ofvarious operations of the image shooting apparatus 1 as a whole, andfeeds those timing control signals to the relevant blocks in the imageshooting apparatus 1. Specifically, the timing control signals are fedto the image shooting portion 11, the video signal processing portion13, the audio signal processing portion 15, the compression portion 16,the decompression portion 19, and the CPU 23. The timing control signalsinclude a vertical synchronizing (v-sync) signal Vsync and a horizontalsynchronizing (h-sync) signal Hsync.

The CPU 23 controls the different blocks in the image shooting apparatus1 in a centralized fashion. The operated portion 26 is operated by theuser to receive instructions. The instructions received by the operatedportion 26 are transmitted to the CPU 23. The SDRAM 17 functions as aframe memory. To the SDRAM 17, different blocks in the image shootingapparatus 1 record various kinds of data (digital signals) temporarilywhenever necessary for signal processing. Such recording is achieved byan SDRAM controller (unillustrated) that controls writing and reading ofdata to and from the SDRAM 17.

The memory card 18 is an external recording medium, for example an SD(secure digital) memory card. The memory card 18 is removable from theimage shooting apparatus 1. The contents of the memory card 18 can befreely read by an external personal computer or the like via thecontacts on the memory card 18 or via a communication connector(unillustrated) provided in the image shooting apparatus 1. In thisembodiment, a memory card 18 is taken up as an example of an externalrecording medium; in practice, it is possible to use any one or morerecording media that allow random access, examples including asemiconductor memory, a memory card, an optical disk, and a magneticdisk.

FIG. 2 is an internal configuration diagram of the image shootingportion 11 shown in FIG. 1. The image shooting portion 11 includes anoptical system 35, an aperture stop 32, an image sensing device 33, anda driver 34. The optical system 35 includes a plurality of lensesincluding a zoom lens 30 and a focus lens 31. The driver 34 includes amotor for moving the zoom lens 30 and the focus lens 31 and foradjusting the aperture of aperture stop 32.

The light incoming from a subject (shooting object) passes through thezoom lens 30 and the focus lens 31 included in the optical system 35,and then passes through the aperture stop 32 to reach the image sensingdevice 33. The TG 22 generates driving pulses for driving the imagesensing device 33 in synchronism with the previously mentioned timingcontrol signals, and feeds those driving pulses to the image sensingdevice 33.

The image sensing device 33 is, for example, a CCD (charge-coupleddevice) or CMOS (complementary metal oxide semiconductor) image sensor.Through photoelectric conversion, the image sensing device 33 convertsthe optical image incoming through the optical system 35 and theaperture stop 32 into an electric signal, which the image sensing device33 then feeds to the AFE 12. More specifically, the image sensing device33 has a plurality of pixels (photoreceptive pixels, unillustrated)arrayed two-dimensionally in a matrix. During image sensing, each pixelstores electric charge whose amount is commensurate with the durationfor which the pixel has been exposed to light. In synchronism with thedriving pulses from the TG 22, an electric signal whose intensity isproportional to the amount of electric charge so stored is fedsequentially to the AFE 12.

The image sensing device 33 is a single-panel image sensing devicecapable of color image sensing. Each pixel of the image sensing device33 is provided with a red (R), green (G), or blue (B) color filter(unillustrated). The image sensing device 33 may be a three-panel imagesensing device.

The AFE 12 includes an amplifier circuit (unillustrated) and an A/D(analog-to-digital) conversion circuit (unillustrated). The amplifiercircuit amplifies the output signal of the image shooting portion 11(i.e., the output signal of the image sensing device 33), which is theabove-mentioned electric signal, which is analog. The A/D conversioncircuit converts the so amplified electric signal into a digital signal.Converted into a digital signal by the AFE 12, the output signal of theimage shooting portion 11 is fed sequentially to the video signalprocessing portion 13. Based on the level of the output signal of theimage shooting portion 11, the CPU 23 controls the amplification factorof the amplifier circuit.

In the following description, the signal outputted from the imageshooting portion 11, and hence from the AFE 12, i.e., the signalrepresenting the subject, is called the sensed-image signal.

FIG. 3 is an internal block diagram of the video signal processingportion 13. The video signal processing portion 13 includes amovie/still image processing portion 41, an AF value detection portion42, an AE value detection portion 43, a motion detection portion 44, athumbnail generation portion 45, and a face area detection portion 46.

Based on the sensed-image signal from the AFE 12, the movie/still imageprocessing portion 41 generates a video signal representing the image(sensed image) obtained through image sensing by the image shootingportion 11, and then feeds the video signal to the compression portion16. The video signal is composed of a luminance signal Y representingthe brightness of the sensed image and color-difference signals U and Vrepresenting the color of the sensed image. The movie/still imageprocessing portion 41 generates both a video signal of a movie and avideo signal of a still image.

The microphone 14 converts sounds (voices) from around into an analogelectric signal, and outputs the electric signal. The audio signalprocessing portion 15 converts the electric signal (analog audio signal)outputted from the microphone 14 into a digital signal. This digitalsignal is then fed, as an audio signal representing the sounds collectedby the microphone 14, to the compression portion 16.

The compression portion 16 compresses the video signal from the videosignal processing portion 13 (the movie/still image processing portion41) by a predetermined compression method: it compresses movies by, forexample, a compression method complying with the MPEG (Moving PictureExperts Group) standard, and compresses still images by, for example, acompression method complying with the JPEG (Joint Photographic ExpertsGroup) standard. When a movie or still image is shot, its compressedvideo signal is fed to the memory card 18.

For example, wherever necessary, the size of the images constituting amovie, which are individually shot, is reduced, for example, throughthinning-out by, for example, the movie/still image processing portion41. For example, a still image is not subjected (but may be subjected)to such size reduction.

The compression portion 16 compresses the audio signal from the audiosignal processing portion 15 by a predetermined compression method, suchas one complying with the AAC (Advanced Audio Coding) standard. When amovie is shot, the video signal from the video signal processing portion13 and the audio signal from the audio signal processing portion 15 arecompressed by the compression portion 16, while they are temporallyassociated with each other, and are then fed to the memory card 18.

The record button 26 a is a push-button switch that is operated by theuser to enter an instruction to start or stop shooting of a movie(moving picture). The shutter button 26 b is a push-button switch thatis operated by the user to enter an instruction to shoot a still image(still picture). When the record button 26 a is operated, a movie startsor stops being shot; when the shutter button 26 b is operated, a stillimage is shot. For each frame, one frame image is acquired. The durationof each frame is, for example, 1/60 seconds. Thus, a series of frameimages acquired at a cycle of 1/60 seconds (a stream image) constitutesa movie.

The image shooting apparatus 1 operates in different modes, including ashooting mode in which it can shoot movies and still images and aplayback mode in which it plays back movies and still images stored inthe memory card 18 on the display portion 27. The playback mode includesa thumbnail image display mode in which thumbnail images associated withthe movies and still images stored in the memory card 18 are played backand displayed on the display portion 27. The different modes areswitched as the operation keys 26 c are operated.

In the shooting mode, when the user presses the record button 26 a,under the control of the CPU 23, the video signal of the framessucceeding the press is, along with the corresponding audio signal,sequentially recorded to the memory card 18 via the compression portion16. That is, along with the audio signal, the shot images of the frames(i.e., the frame images) are stored sequentially in the memory card 18.After the start of shooting of the movie, when the user presses therecord button 26 a again, the movie stops being shot. That is, the videosignal and the audio signal stop being recorded to the memory card 18,and thus the shooting of the movie is completed.

On the other hand, in the shooting mode, when the user presses theshutter button 26 b, a still image is shot. Specifically, under thecontrol of the CPU 23, the video signal of one frame immediately afterthe press is recorded, as a video signal representing a still image, tothe memory card 18 via the compression portion 16. A still image can beshot simultaneously while a movie is being shot. In this case, based onthe sensed-image signal of the same frame, signal processing for themovie and that for the still image are performed concurrently.Alternatively, a single circuit may be shared on a time-division basisso as to perform signal processing for a movie and that for a stillimage at different timing. For example, signal processing for a stillimage is performed after shooting of a movie. In this case, for example,the sensed-image signal (shot image) needed for later signal processingis temporarily stored in the SDRAM 17.

In the playback mode, when the user operates the operation keys 26 c ina predetermined way, the compressed video signal representing a movie orstill image recorded in the memory card 18 is fed to the decompressionportion 19. The decompression portion 19 decompresses the video signaland then feeds it to the image output circuit 20. Moreover, in theplayback mode, generally, irrespective of whether or not a movie orstill image is being shot, the video signal processing portion 13continues generating a video signal, which is kept fed to the imageoutput circuit 20.

The image output circuit 20 converts the video signal, fed to it indigital form, into a video signal in a format that can be displayed onthe display portion 27 (e.g., an analog video signal) and then outputsit. The display portion 27 is a display device such as a liquid crystaldisplay, and displays an image according to the video signal outputtedfrom the image output circuit 20. That is, the display portion 27displays an image based on the sensed-image signal currently beingoutputted from the image shooting portion 11 (the image representing thesubject currently being shot) or a movie (moving picture) or still image(still picture) recorded in the memory card 18.

When a movie is played back in the playback mode, the correspondingcompressed audio signal recorded in the memory card 18 is also fed tothe decompression portion 19. The decompression portion 19 decompressesthe audio signal and then feeds it to the sound output circuit 21. Thesound output circuit 21 converts the audio signal, fed to it in digitalform, into an audio signal in a format from which the loudspeaker 28 canplay back (e.g., an analog audio signal) and then outputs it to theloudspeaker 28. The loudspeaker 28 reproduces sounds (voices) from theaudio signal from the sound output circuit 21 and outputs the sounds tothe outside.

The display portion 27 and the loudspeaker 28 may be thought of as beingincorporated in an external television monitor or the like. In thatcase, the video signal outputted from the image output circuit 20 andthe audio signal outputted from the sound output circuit 21 are fed tothe external television monitor or the like via an unillustratedconnector.

Next, with reference to FIGS. 2 and 3, the operation of the imageshooting portion 11 and the video signal processing portion 13 will bedescribed in more detail. The image shooting apparatus 1 is equippedwith a so-called autofocus (automatic focusing) capability, whereby theposition of the focus lens 31 is automatically controlled so that theoptical image representing the subject is focused on the image sensingsurface (light receiving surface) of the image sensing device 33.Ideally, this capability allows the points at which the optical imagerepresenting the subject is focused coincide with points on the imagesensing surface of the image sensing device 33.

The autofocus capability can be realized by various methods. Forexample, a predetermined high-frequency component is extracted from theluminance signal contained in the video signal and, according to thelevel (intensity) of that high-frequency component, the position of thefocus lens 31 is controlled so that the optical image representing thesubject is focused on the image sensing surface of the image sensingdevice 33. The autofocus capability may be realized with adistance-measuring sensor (unillustrated) or the like.

Autofocus is achieved mainly by the AF value detection portion 42 shownin FIG. 3, the CPU 23 shown in FIG. 1, and the driver 34 shown in FIG.2. Based on a focusing control signal that is fed from the CPU 23 tokeep the level (intensity) of the above-mentioned high-frequencycomponent at (close to) its maximum value, the driver 34 moves the focuslens 31 along the optical axis, which is perpendicular to the imagesensing surface, so that the optical image of the subject (shootingobject) is focused on the image sensing surface (light receivingsurface) of the image sensing device 33.

FIG. 4 is an internal block diagram of the AF value detection portion42. The AF value detection portion 42 includes an extraction portion 51,a HPF (high-pass filter) 52, and a totaling portion 53.

The extraction portion 51 extracts the luminance signal from the videosignal generated by the movie/still image processing portion 41 or fromthe sensed-image signal from the AFE 12. Here, the luminance signal isextracted only from within a prescribed focus detection area in theimage. The focus detection area is defined, for example, to cover a partof the image around its center. From the luminance signal extracted bythe extraction portion 51, the HPF 52 extracts a predeterminedhigh-frequency component.

The totaling portion 53 totalizes the high-frequency component extractedby the HPF 52 and thereby calculates an AF evaluation value commensuratewith the degree of contrast within the focus detection area in theimage. The AF evaluation value is calculated frame by frame and is fedsequentially to the CPU 23. The AF evaluation value is roughlyproportional to the degree of contrast, the former increasing as thelater increases.

The CPU 23 temporarily stores the AF evaluation value fed to it for oneframe after another, and controls, via the driver 34, the position ofthe focus lens 31 by so-called hill-climbing calculation in such a waythat the AF evaluation value remains at (close to) its maximum value. Asthe focus lens 31 is moved, the degree of contrast in the image varies,and accordingly the AF evaluation value varies. The CPU 23 controls, viathe driver 34, the position of the focus lens 31 in that direction inwhich the AF evaluation value increases. As a result, as long as theoptical image remains the same, the degree of contrast within the focusdetection area is kept at (close to) its maximum value.

The image shooting apparatus 1 is also equipped with a so-calledautoiris (automatic irising) capability, whereby the brightness of theshot image is kept (substantially) constant. Autoiris is realized mainlyby the AE value detection portion 43 shown in FIG. 3, the CPU 23 shownin FIG. 1, and the driver 34 shown in FIG. 2.

The AE value detection portion 43 extracts the luminance signal from thevideo signal generated by the movie/still image processing portion 41 orfrom the sensed-image signal from the AFE 12. Here, the luminance signalis extracted, for example, from all over the image. The AE valuedetection portion 43 totalizes the extracted luminance signal for oneentire image and thereby calculates an AE evaluation value proportionalto the brightness of the image. The AE evaluation value is calculatedframe by frame and is fed sequentially to the CPU 23.

The CPU 23 controls, via the driver 34, the aperture (how large is theopening) of the aperture stop 32 in such a way that the AE evaluationvalue fed to the CPU 23 for one frame after another remains at aconstant value. As long as the optical image incoming through theoptical system 35 remains the same, as the aperture of the aperture stop32 increases, the amount of light incident on the image sensing device33 per unit time increases, and accordingly the level (value) of theluminance signal increases. In a case where even with the aperture ofthe aperture stop 32 at its maximum the AE evaluation value is less thanthe above-mentioned constant value, the amplification factor of theamplifier circuit in the AFE 12 is so adjusted as to keep the AEevaluation value constant.

Moreover, when the operation keys 26 c are operated in a predeterminedway, the CPU 23 moves, via the driver 34, the zoom lens 30 along theoptical axis so as to thereby vary the angle of view at which the imageshooting portion 11 performs shooting (in other words, so as to therebyenlarge or reduce the image of the subject formed on the image sensingsurface of the image sensing device 33).

The video signal processing portion 13 shown in FIG. 1 includes themotion detection portion 44 (see FIG. 3). Based on the sensed-imagesignal, the motion detection portion 44 detects the motion of thesubject among the images of consecutive frames. This detection isachieved, for example, by the well-known representative point matchingmethod. Based on the detected motion (e.g., represented by a vector),so-called camera shake correction is performed.

When a still image is shot, under the control of the CPU 23, thethumbnail generation portion 45 shown in FIG. 3 generates a thumbnailimage of the still image based on the sensed-image signal at the timingthat the still image is shot. This thumbnail image is a reduced image ofa single still image (still picture) that has been shot and recorded,reduced, for example, through thinning-out. A thumbnail image of a shotstill image is, with association established between them, compressed bythe compression portion 16 (e.g., in compliance with the JPEG standard)and recorded to the memory card 18. A thumbnail image associated with ashot still image is called a still-image thumbnail (meaning “a thumbnailof a still image”).

On the other hand, when a movie is shot, under the control of the CPU23, the thumbnail generation portion 45 generates a thumbnail image ofthe movie based on the sensed-image signal at predetermined timing. Thisthumbnail image is a reduced image of the image (a one-frame-worthimage) of one of the frames constituting the movie being shot, reduced,for example, through thinning-out. A thumbnail image of a shot movie is,(in principle) with association established between them, compressed bythe compression portion 16 (e.g., in compliance with the JPEG standard)and recorded to the memory card 18. A thumbnail image generated to berecorded in association with a shot movie is called a movie thumbnail(meaning “a thumbnail of a movie”). In a case where the pixel size of amovie is comparatively small, the image of one of the framesconstituting a shot movie may itself be used as a movie thumbnail.

A movie thumbnail may be generated at any timing. For example, a moviethumbnail may be generated by receiving the sensed-image signal from theAFE 12 during shooting of a movie is being shot. Instead, while a movieis being shot, an image from which to generate a movie thumbnail latermay be selected so that from that image a movie thumbnail is generatedafterwards (e.g., when one needs to be displayed on the display portion27). Anyway, the sensed-image signal from which a given movie thumbnailis generated is the same. This embodiment deals with a case where, whilea movie is being shot, a movie thumbnail is generated and stored in thememory card 18. Likewise, a still-image thumbnail may be generated atany timing.

In the thumbnail image display mode, movie thumbnails and still-imagethumbnails stored in the memory card 18 are decompressed by thedecompression portion 19 and then converted by the image output circuit20 so as to be displayed on the display portion 27.

FIG. 5 shows an example of the screen displayed on the display portion27 in the thumbnail image display mode. In FIG. 5, the display area onthe display portion 27 is divided into four parts, with thumbnail imagesTN1, TN2, TN3, and TN4 displayed in the upper left, upper right, lowerleft, and lower right parts of the display area respectively. If morethumbnail images are stored in the memory card 18, operating theoperation keys 26 c in a predetermined way makes them appear on thescreen. The thumbnail images TN2 and TN3 bear a mark 71 indicating thatthey are movie thumbnails. Thus, the thumbnail images TN2 and TN3 aremovie thumbnails, while the thumbnail images TN1 and TN4 are still-imagethumbnails.

As shown in FIG. 5, a cursor 72 appears on the screen. The cursor 72moves across the screen as the operation keys 26 c are operated. FIG. 5shows a state in which the thumbnail image TN3 is being selected by thecursor 72. The number, such as “001”, appearing in a lower right part ofeach thumbnail image is its file number.

When a thumbnail image is being selected by the cursor 72, operating thekeys in a predetermined way causes the movie or still image associatedwith that thumbnail image to be read from the memory card 18. The movieor still image is then displayed over the entire screen on the displayportion 27. For example, when the keys are so operated as to start theplayback of the movie corresponding to the thumbnail image TN3, thescreen on the display portion 27 changes from FIG. 5 to FIG. 6, and themovie corresponding to the thumbnail image TN3 is played back over theentire screen on the display portion 27. In this state, when the keysare so operated as to stop the playback, the screen returns to FIG. 5.

Method for Generating a Movie Thumbnail

Next, how a movie thumbnail is generated will be described. FIG. 7 is aflow chart showing the procedure for generating a movie thumbnail.Unless otherwise stated, the following description of this embodimentfocuses on a given single movie.

When a power switch (unillustrated) provided in the image shootingapparatus 1 is operated so that electric power starts to be supplied tothe different blocks in the image shooting apparatus 1, the TG 22 startsgenerating a vertical synchronizing (v-sync) signal at a predeterminedcycle (e.g., 1/60 seconds). First, in step S1, whether or not the TG 22has just outputted a vertical synchronizing signal is checked. The TG 22outputs the vertical synchronizing signal at the start of every frame.

As long as no vertical synchronizing signal is found to have just beenoutputted (“No” in step S1), step S1 is repeated; if a verticalsynchronizing signal is found to have just been outputted (“Yes” in stepS1), then, in step S2, whether or not the image shooting apparatus 1 isrecording (shooting a movie) is checked. If so (“Yes” in step S2), theprocedure proceeds to step S7; if not (“No” in step S2), the procedureproceeds to step S3. In step S3, whether or not the record button 26 ahas been pressed in the shooting mode is checked. If so, (“Yes” in stepS3), the procedure proceeds to step S4; if not (“No” in step S3), theprocedure returns to step S1. In this way, before recording is started,the loop through steps S1, S2, and S3 is executed repeatedly.

In step S4, the CPU 23 defines two flags F0 and F1, each taking thevalue “0” or “1” at a time, and substitutes “0” in both of them (i.e.,resets them). The flag F0 is reset every time recording is started. Whatthe flag F1 serves for will be described later.

After step S4, in step S5, the thumbnail generation portion 45 generatesa movie thumbnail based on the one-screen-worth sensed-image signalcurrently being outputted from the AFE 12. Subsequent to step S5, instep S6, the CPU 23 creates a header file. The header file contains, inaddition to the movie thumbnail generated in step S5, various kinds ofinformation such as the shooting date and time and the file number. Theheader file is then recorded to the SDRAM 17. This embodiment deals witha case where one header file contains one movie thumbnail.

After step S6, back in step S1, the generation of a verticalsynchronizing signal is waited for again. When step S2 is reachedthrough steps S4 to S6, the image shooting apparatus 1 is recording, andaccordingly the procedure then proceeds to step S7 (“Yes” in step S2).

In step S7, the CPU 23 creates a stream image file in which to store theseries of images representing the shot movie (i.e., a stream image), andrecords the stream image file to the memory card 18. To the stream imagefile is additionally recorded sequentially the video signal (compressedvideo signal) representing the images of the frames of the moviecurrently being shot, along with the corresponding audio signal(compressed audio signal). Eventually, at the end of recording, thestream image file contains the video signal representing the shot imagesof all the frames after the start until the end of recording along withthe corresponding audio signal.

After step S7, in step S8, whether or not the user has pressed therecord button 26 a again is checked, that is, whether or not aninstruction to stop recording has been entered is checked. If not (“No”in step S8), the procedure proceeds to step S10. Until an instruction tostop recording is entered, the loop through the sequence of steps S10 toS15 and through steps S1, S2, S7, and S8 is executed repeatedly. Thisloop is gone through once every frame.

If, in step S8, an instruction to stop recording is found to have beenentered (“Yes” in step S8), the procedure proceeds to step S9, where theheader file created in step S6 is additionally recorded to the streamimage file created in step S7. This allows the two files to beassociated with each other, and thus the movie thumbnail generated instep S5 and the movie contained in the stream image file are associatedwith each other, or (as will be described later) the movie thumbnailgenerated in step S13, which will be described later, and the moviecontained in the stream image file are associated with each other. Afterstep S9, the procedure returns to step S1, bringing the image shootingapparatus 1 back into the state in which it can accept an instruction tostart shooting of a new movie.

Now, a description will be given of the operations performed in stepsS10 to S15, which constitute the distinctive features of the invention.

In step S10, whether or not the flag F0 is set is checked, that is,whether or not the flag F0 is “1” is checked. If the flag F0 is “1”(“Yes” in step S10), the procedure returns to step S1; if the flag F0 is“0” (“No” in step S10), the procedure proceeds to S11. During shootingof one movie, when steps S13 and S14 are gone through once, the check instep S10 always results in “Yes”.

In step S11, the CPU 23 checks whether or not a predetermined triggeringcondition is fulfilled. What a triggering condition is will be describedin detail later. If the flag F0 is “0”, step S11 is executed for eachframe during movie shooting. If the triggering condition is notfulfilled (“No” in step S11), the procedure proceeds to step S15, where“0” is substituted in the flag F1, and then returns to step S1. If thetriggering condition is fulfilled (“Yes” in step S11), the procedureproceeds to step S12, where whether or not the flag F1 is “1” ischecked. If the flag F1 is “1” (“Yes” in step S12), the procedurereturns to step S1; if the flag F1 is “0” (“No” in step S12), theprocedure proceeds to step S13.

In step S13, based on the one-screen-worth sensed-image signal currentlybeing outputted from the AFE 12, a movie thumbnail is generated. Thus,based on the sensed-image signal (sensed image) of the frame whoseduration includes the timing at which the triggering condition isfulfilled in step S11, or of the immediately succeeding frame, a moviethumbnail is generated. A movie thumbnail to be generated in step S13may instead be generated based on the sensed-image signal (sensed image)of the frame several frames before or after the triggering condition isfulfilled.

After step S13, in step S14, the movie thumbnail existing in the headerfile created in step S6 is replaced with the movie thumbnail generatedin step S13; moreover, “1” is substituted in both the flags F0 and F1.The procedure then returns to step S1.

Step S10 may be omitted. In that case, if, in step S8, no instruction tostop recording is found to have been entered (“No” in step S8), theprocedure proceeds directly to step S11. In a case where step S10 isomitted, even after steps S13 and S14 are executed, the triggeringcondition is not fulfilled, and thus step S15 is gone through; hence,steps S13 and S14 are allowed to be executed again. In this case, everytime step S14 is executed for the second or any subsequent time, themovie thumbnail existing in the header file is replaced with the“latest” movie thumbnail generated in step S13.

As will be understood from the procedure described above, the moviethumbnails generated in steps S5 and S13 become candidates for the moviethumbnail to be associated with a shot movie. If the triggeringcondition is not fulfilled even once during shooting of a movie, themovie thumbnail generated in step S5 eventually becomes the moviethumbnail associated with the movie.

If, in step S11, the triggering condition is fulfilled, the moviethumbnail generated in step S13 eventually becomes associated with theshot movie. In a case where step S10 is omitted, the latest moviethumbnail generated in step S13 eventually becomes associated with theshot movie.

The above-mentioned triggering condition is so defined that the moviethumbnail generated in step S13 aptly represents the shot movie. Now,different methods for checking whether or not a triggering condition isfulfilled in step S11 will be described below as a first to a fifthcheck method. FIG. 8 shows typical examples of different triggeringconditions, corresponding to the first to fifth check methodsrespectively.

First Check Method: First, the first check method will be described. Thetriggering condition whose fulfillment is checked in step S11 when thefirst check method is adopted will be called the first triggercondition. If the first triggering condition is fulfilled, the procedureproceeds to step S12; if not, the procedure proceeds to step S15.

In a case where the first check method is adopted, in step S11, forexample, whether or not “no change in angle of view has been made byzooming-in or zooming-out (i.e. the angle of view has been fixed) for apredetermined period T1 or longer after immediately previous zooming-in”is checked as a check of whether or not the first triggering conditionis fulfilled. This check is made with respect to the current moment(current frame). The period T1 is, for example, a few seconds (e.g., oneto two seconds).

For example, suppose that, as shown in FIG. 9, after a movie starts tobe shot, zooming-in is performed for the first time, and thenimmediately thereafter, specifically before a period T1 passesthereafter, zooming-out is performed; then, further afterwards,zooming-in is performed for the second time. In this case, whether ornot a period T1 has passed is checked with respect to the end of thesecond-time zooming-in (the immediately previous zooming-in).

Zooming-in is the operation whereby the image of the subject formed onthe image sensing surface of the image sensing device 33 is enlarged; aszooming-in is performed, the angle of view at which the image shootingportion 11 performs shooting decreases. Zooming-out is the operationwhereby the image of the subject formed on the image sensing surface ofthe image sensing device 33 is reduced; as zooming-out is performed, theangle of view at which the image shooting portion II performs shootingincreases. Zooming-in and zooming-out are performed when the operationkeys 26 c are operated in predetermined ways.

The user often enlarges the subject he is aiming at, for example aperson, by zooming in on it. As soon as the user knows he has zoomed into an adequate angle of view, he stops changing the angle of view. Animage shot in this state is likely to be a representative one in whichthe subject being aimed at appears large enough. Thus, adopting thefirst check method helps obtain thumbnail images that aptly representmovies, and thus helps facilitate retrieval of the desired movie.

The first triggering condition may be modified to whether or not “nochange in angle of view has been made by zooming-in or zooming-out (i.e.the angle of view has been fixed) for a predetermined period T1 orlonger after immediately previous zooming-out”.

Second Check Method: Next, the second check method will be described.The triggering condition whose fulfillment is checked in step S11 whenthe second check method is adopted will be called the second triggercondition. If the second triggering condition is fulfilled, theprocedure proceeds to step S12; if not, the procedure proceeds to stepS15.

In a case where the second check method is adopted, in step S11, whetheror not “the focus, once achieved, have been kept (substantially) lockedfor a predetermined period or longer” is checked. More specifically, instep S11, for example, whether or not “the width of variation of theposition of the focus lens 31 has remained smaller than or equal to apredetermined threshold value for a predetermined period T2 or longer”is checked as a check of whether or not the second triggering conditionis fulfilled. This check is made with respect to the current moment(current frame). The period T2 is, for example, a few seconds (e.g., oneto two seconds).

As described earlier, based on the AF evaluation value calculated frameby frame, the CPU 23 controls, via the driver 34, the position of thefocus lens 31 in such a way that the optical image representing thesubject is focused on the image sensing surface (light receivingsurface) of the image sensing device 33. Thus, naturally, the CPU 23knows the position of the focus lens 31. The position of the focus lens31 is, for example, its position with respect to the image sensingsurface of the image sensing device 33.

Now, with reference to FIG. 10, an example of how to check whether ornot the second triggering condition is fulfilled will be described indetail. In FIG. 10, curves 75 and 76 represent the temporal variation ofthe AF evaluation value and of the position of the focus lens 31 (e.g.,the distance from the focus lens 31 to the image sensing surface),respectively, during shooting of a movie. In FIG. 10, at time t1, the AFevaluation value becomes roughly equal to the maximum value of ahill-climbing curve; thereafter, the AF evaluation value remains thereuntil time t2. The period between times t1 and t2 equals T2.

At time t2, the CPU 23 compares the width of variation of the positionof the focus lens 31 (the width across which it has been varying) duringthe period between times t1 and t2 with a prescribed reference valueB_(REF). If the former is smaller than or equal to the latter (B_(REF)),the second triggering condition is judged to be fulfilled; otherwise,the second triggering condition is judged to be not fulfilled. To enablethis judgment, the CPU 23 keeps, in the SDRAM 17, frame-by-frameinformation on the position of the focus lens 31 for the past periodequal to T2.

In a case where the focus lens 31 can be kept at a completely fixedposition when it is focused, the reference value B_(REF) may be setequal to zero. In that case, the second triggering condition is whetheror not “the position of the focus lens 31 has remained fixed for apredetermined period T2 or longer”. The position of the focus lens 31may be so controlled as to be kept fixed as long as the AF evaluationvalue varies within a certain width (which equals, for example, areference value A_(REF), which will be described later). In that case,the reference value B_(REF) is set equal to zero.

As shown in FIG. 10, the AF evaluation value and the position of thefocus lens 31 vary in a coordinated fashion. Thus, the check in step S11may be made based on the AF evaluation value. Specifically, for example,at time t2, the CPU 23 compares the width of variation of the AFevaluation value (the width across which it has been varying) during theperiod between times t1 and t2 with a prescribed reference valueA_(REF). If the former is smaller than or equal to the latter (A_(REF)),the procedure proceeds from step S11 to step S12; otherwise, theprocedure proceeds from step S11 to step S15. In that case, to enablesuch judgment, the CPU 23 keeps, in the SDRAM 17, the frame-by-frame AFevaluation value for the past period equal to T2.

In this way, the triggering condition whose fulfillment is checked instep S11 may be whether or not “the width of variation of the AFevaluation value has remained smaller than or equal to a predeterminedreference value A_(REF) for a predetermined period T2 or longer”.Considering that the AF evaluation value and the position of the focuslens 31 vary in a coordinated fashion, this triggering condition isequivalent to the second triggering condition.

After starting to shoot a movie, the user tends to move the imageshooting apparatus 1 around while paying attention to the composition ofthe movie being shot. Once a satisfactory composition is obtained, theuser holds the image shooting apparatus 1 in a position (substantially)fixed relative to the subject. In this state, usually the focus islocked so that the image shooting apparatus 1 captures the subject theuser is aiming at. Thus, adopting the second check method helps obtainthumbnail images that aptly represent movies, and thus helps facilitateretrieval of the desired movie.

Third Check Method: Next, the third check method will be described. Thetriggering condition whose fulfillment is checked in step S11 when thethird check method is adopted will be called the third triggercondition. If the third triggering condition is fulfilled, the procedureproceeds to step S12; if not, the procedure proceeds to step S15.

In a case where the third check method is adopted, in step S11, whetheror not what appeared in the shot images has remained (substantially)motionless for a predetermined period or longer is checked. Morespecifically, in step S11, for example, whether or not “the magnitude ofmotion within the motion detection area has remained smaller than orequal to a predetermined threshold value for a predetermined period T3or longer” is checked as a check of whether or not the third triggeringcondition is fulfilled. This check is made with respect to the currentmoment (current frame). The motion detection area is defined in the shotimage of each frame constituting a movie, so as to cover the whole or apart of the shot image (it may be thought of as an area covering thewhole or a part of the image-sensing area of the image sensing device33). The period T3 is, for example, a few seconds (e.g., one to twoseconds).

Now, with reference to FIG. 11, an example of how to check whether ornot the third triggering condition is fulfilled will be described indetail. FIG. 11 shows detection blocks defined in a shot image by themotion detection portion 44 shown in FIG. 3. The motion detectionportion 44 defines nine detection blocks BL1 to BL9 in the shot image ofeach frame. Together the nine detection blocks BL1 to BL9 form theabove-mentioned “motion detection area”.

Through comparison among shot images acquired one after another, themotion detection portion 44 detects a motion vector in each of thedetection blocks BL1 to BL9 by the well-known representative pointmatching method. This detection of motion vectors is performed frame byframe. The motion vector in the detection block BL1 represents themotion within the detection block BL1 in the image; likewise, the motionvectors in the other detection blocks BL2 to BL9 respectively representthe motion there. The motion vectors detected in the detection blocksBL1 to BL9 are called the motion vectors VC1 to VC9 respectively.

Based on a motion evaluation value based on the magnitudes of the motionvectors VC1 to VC9 detected frame by frame, the CPU 23 checks whether ornot the third triggering condition is fulfilled. The motion evaluationvalue is calculated frame by frame. The motion evaluation value is, forexample, the average value or the totalized value of the magnitudes ofthe motion vectors VC1 to VC9. The magnitudes of the motion vectors VC1to VC9 may themselves be used as motion evaluation values. In that case,for each frame, nine motion evaluation values are obtained.

In FIG. 12, a curve 77 represents the temporal variation of the motionevaluation value during shooting of a movie. Suppose that, at time t3,the motion evaluation value, which has been greater than a predeterminedreference value C_(REF) up to that point, becomes smaller than or equalto the reference value C_(REF), and thereafter continuously remains sountil time t4. The period between times t3 and t4 equals T3.

At time t4, the CPU 23 compares every motion evaluation value during theperiod between times t3 and t4 with the reference value C_(REF). If theformer has continuously remained smaller than or equal to the latter(C_(REF)), the third triggering condition is judged to be fulfilled;otherwise, the third triggering condition is judged to be not fulfilled.To enable this judgment, the CPU 23 keeps, in the SDRAM 17, theframe-by-frame motion evaluation value for the past period equal to T3.

As will be understood from the foregoing, the third triggering conditionis, put otherwise, whether or not “a motion evaluation value based onthe magnitude of motion within the motion detection area in a movie hascontinuously remained smaller than or equal to a predetermined thresholdvalue for a predetermined period T3 or longer”.

A condition where no motion is observed among the shot images of a moviefor a certain period or longer is supposed to correspond to a conditionwhere a subject being aimed at, such as a person, is being captured in astationary state. Thus, adopting the third check method helps obtainthumbnail images that aptly represent movies, and thus helps facilitateretrieval of the desired movie.

In a case where the image shooting apparatus 1 is held in the hands,so-called camera shake causes the subject in the image to move slightly.To avoid complete unfulfillment of the third triggering condition due tohand shake, the above-mentioned threshold value is set adequatelythrough experiments or the like using an actual image shootingapparatus.

The detection of (the magnitude of) motion in the motion detection areacan be achieved by various methods other than the representative pointmatching method specifically mentioned above.

For example, as is well known, the brightness (luminance signal) may becompared among the frames constituting a movie, detection block bydetection block, so that, based on how the brightness varies in eachdetection block, (the magnitude of) motion within the motion detectionarea is detected. For another example, as is well known, the color(which is identified based on the video signal) may be compared amongthe frames constituting a movie, detection block by detection block, sothat, based on how the color varies in each detection block, (themagnitude of) motion within the motion detection area is detected.

Fourth Check Method: Next, the fourth check method will be described.The triggering condition whose fulfillment is checked in step S11 whenthe fourth check method is adopted will be called the fourth triggercondition. If the fourth triggering condition is fulfilled, theprocedure proceeds to step S12; if not, the procedure proceeds to stepS15.

The fourth check method utilizes a face area detection capability, thatis, a capability of detecting the area of a person's face appearing inthe shot image of each frame. To achieve face area detection, the facearea detection portion 46 is included in the video signal processingportion 13 (see FIG. 3). In a case where the fourth check method isadopted, in step S11, for example, whether or not “the size of thedetected face area is larger than or equal to a predetermined threshold(reference size)” is checked as a check of whether or not the fourthcheck method is fulfilled.

Face area detection can be achieved by various methods. For example, theface area detection portion 46 recognizes the size of a face area byextracting a flesh-colored area from a shot image, as is well known.Specifically, for example, the face area detection portion 46 extractsfrom the shot images of the frames constituting a movie an area, calleda face area, having a video signal classified as representing a fleshcolor, and then, based on the size (e.g., the area) of that area,calculates (detects) the size of the face area. Here, the extraction ofa relevant area and the detection of the size of a face area areperformed frame by frame. What video signal to classify as representinga flesh color is prescribed.

The size of a face area may also be detected by pattern matching, as iswell known. In that case, information on various patterns of face areasis previously stored in a memory in the image shooting apparatus 1, andthose patterns are compared with a shot image to detect a face area andits size.

In practice, for example, the face area detection portion 46 calculatesa face area value commensurate with the size of a face area frame byframe and transmits it sequentially to the CPU 23. If the CPU 23receives a face area value larger than or equal to a predeterminedthreshold value, it judges the fourth triggering condition to befulfilled; otherwise, the CPU 23 judges the fourth triggering conditionto be not fulfilled. The face area value increases as the size of thedetected face area increases.

A condition where a face appears comparatively large in an image issupposed to correspond to a condition where the face of a person beingaimed at by the user appears large. Thus, adopting the fourth checkmethod helps obtain thumbnail images that aptly represent movies, andthus helps facilitate retrieval of the desired movie.

An upper limit may be set on the size of the face area, or the face areavalue, that fulfills the fourth triggering condition. Specifically, inthat case, “if the size of the detected face area or the face area valueis larger than or equal to a first threshold value but smaller than orequal to a second threshold value”, in other words “if the size of thedetected face area or the face area value is within a predeterminedrange”, the procedure proceeds to step S12, and otherwise it proceeds tostep S15. Here, the second threshold value is greater than the firstthreshold value.

If a thumbnail image is generated based on an image in which a faceoccupies an extremely large part of it, the thumbnail image represents amovie rather inaptly. It is out of this consideration that an upperlimit may be set as mentioned above.

Fifth Check Method: Next, the fifth check method will be described. Thetriggering condition whose fulfillment is checked in step S11 when thefifth check method is adopted will be called the fifth triggercondition. If the fifth triggering condition is fulfilled, the procedureproceeds to step S12; if not, the procedure proceeds to step S15. Whenthe fifth check method is adopted, step S110 is omitted.

The fifth check method pays attention to the intensity of the soundcollected by the microphone 14 during movie shooting. The audio signalprocessing portion 15 is capable of sequentially monitoring theintensity of the sound, or the intensity of its frequency component in apredetermined band, collected by the microphone 14 during movieshooting. The detected intensity of sound, or of its frequency componentin a predetermined band, is fed, as a sound intensity value,sequentially to the CPU 23.

Instead of the intensity of sound, the loudness of sound may be detectedso that a value commensurate with the detected loudness of sound, or ofits frequency component in a predetermined band, is used as a soundintensity value. In that case, in the following description, theexpressions “intensity of sound” and “intensity of frequency componentof sound in a predetermined band” are to be read as “loudness of sound”and “loudness of frequency component of sound in a predetermined band”.

The sound intensity value is, for example, the average value, or thepeak value, of the intensity of sound as detected throughout a frame.The sound intensity value may instead be, for example, the averagevalue, or the peak value, of the intensity of frequency component ofsound in a predetermined band as detected throughout a frame. Thus, thesound intensity value is obtained frame by frame. The sound intensityvalue increases as the intensity of sound increases. The above-mentionedfrequency component in a predetermined band is, for example, that in thefrequency band of human voice or in the audible frequency band. Toextract a frequency component in such a predetermined band from theaudio signal fed from the microphone 14, the audio signal processingportion 15 uses a band-pass filter or the like.

The CPU 23 checks whether or not the sound intensity value of thecurrent frame is the greatest among those of all the frames since themovie started to be shot. If the sound intensity value of the currentframe is the greatest, the fifth triggering condition is judged to befulfilled; otherwise, the fifth triggering condition is judged to be notfulfilled.

When a movie is being shot on the occasion of a concert or party, acondition where the intensity of sounds is high is supposed tocorrespond to a condition where the atmosphere is livened up. Thus,adopting the fifth check method helps obtain thumbnail images that aptlyrepresent movies, and thus helps facilitate retrieval of the desiredmovie.

In a case where the fifth check method is adopted, instead of theprocedure for generating a movie thumbnail shown in the flow chart ofFIG. 7, the procedure for generating a movie thumbnail shown in the flowchart of FIG. 13 may be adopted.

The procedure shown in FIG. 13 will now be described. Between FIGS. 7and 13, the operations performed in the steps with the same step numbersare the same. Specifically, the operations performed in steps S1 to S3,S5 to S9, and S13 in FIG. 13 is the same as the operations performed inthe steps with the same step numbers in FIG. 7. In the procedure shownin FIG. 13, step S21 replaces step S4 in FIG. 7, steps S22 and S23replace steps S10 to S12 and S15 in FIG. 7, and step S24 replaces stepS14 in FIG. 7.

In step S3, if the record button 26 a is found to be pressed in theshooting mode, the procedure proceeds to step S21. In step S21, aninitial value Sinit (e.g., zero) is substituted in a variable Smax, andthe procedure proceeds to step S5. In step 8, if no instruction to stoprecording is found to have been entered (“No” in step S8), the procedureproceeds to step S22. Until an instruction to stop recording is entered,the loop of through the sequence of steps S22, S23, S13, and S24 andthrough steps S1, S2, S7 and S8 is executed repeatedly. This loop isgone through once every frame.

In step S22, whether or not the sound intensity value Sin of the currentframe is greater than the variable Smax is checked. If the inequalitySin>Smax holds (“Yes” in step S22), the procedure proceeds to step 23;if not (“No” in step S22), the procedure returns to step S1. In stepS23, the sound intensity value Sin of the current frame is substitutedin the variable Smax, and the procedure proceeds to step S13. In stepS13, a movie thumbnail is generated, and then the procedure proceeds tostep S24. The operation performed in step S24 is the same as theoperation performed in step S14 except that nothing is done with theflags F0 and F1. After step S24, the procedure returns to step S1.

Additional Conditions: Any additional condition may be combined with anyof the first to fifth trigger conditions described above. Specifically,in that case, for example, if the k-th (where k represents an integerbetween 1 and 5) triggering condition described above is fulfilled, thenonly if an additional condition is also fulfilled, the procedureproceeds to step S12; even if the k-th triggering condition isfulfilled, unless the additional condition is fulfilled, the procedureproceeds to step S15.

For example, the first triggering condition described above may becombined with an additional condition that “the image shooting apparatus1 is not being panned or tilted”. Specifically, in that case, if “nochange in angle of view has been made by zooming-in or zooming-out for apredetermined period T1 or longer after immediately previous zooming-in”and in addition if “;the image shooting apparatus 1 is not being pannedor tilted”, then the procedure proceeds to step S12; otherwise, itproceeds to step S15.

This is because an image acquired without the image shooting apparatus 1being panned or tilted, that is, one acquired with the image shootingapparatus 1 held in a fixed position, is supposed to more aptly show thesubject the user is aiming at.

Panning denotes swinging the body (unillustrated) of the image shootingapparatus 1 side to side; tilting denotes swinging it up and down.

In terms of motion, the image shooting apparatus 1 (i.e., its body) is,roughly speaking, in one of the following four states: a stationarystate in which the body of the image shooting apparatus 1 stands still;a hand-shake state in which the body of the image shooting apparatus 1is vibrating finely in indefinite directions because of hand shake orthe like; a panned state in which the image shooting apparatus 1 isbeing panned; and a tilted state in which the image shooting apparatus 1is being tilted. Thus, put otherwise, the above-mentioned additionalcondition is that “the image shooting apparatus 1 is either in thestationary or hand-shake state”.

When checking whether or not the additional condition is fulfilled, theCPU 23 functions as a detector for detecting which of the differentmotion states, namely the stationary, hand-shake, panned, and tiltedstates, the image shooting apparatus 1 is in.

For example, the CPU 23 makes the above check based on an output signalfrom an angular velocity sensor (gyro sensor, unillustrated) thatdetects the angular velocity of the body of the image shooting apparatus1 and whose output thus represents the angular velocity, as is wellknown.

For example, suppose that, with respect to the panning direction, theoutput signal of the angular velocity sensor takes a positive value whenthe body of the image shooting apparatus 1 is swung leftward, takes anegative value when it is swung rightward, and equals zero when it isstanding still. In this case, if the output signal of the angularvelocity sensor equals zero or substantially zero, the stationary stateis recognized; if the output signal of the angular velocity sensorvibrates finely between positive and negative values, the hand-shakestate is recognized; if the output signal of the angular velocity sensorcontinues taking a positive or negative value for a predeterminedperiod, the panned state is recognized. A similar check is made also inthe tilting direction.

The motion state of the image shooting apparatus 1 may also be checkedbased on the result of the detection of motion in the image by themotion detection portion 44 shown in FIG. 3, as is well known. Forexample, the CPU 23 refers to the motion vectors VC1 to VC9 mentionedearlier in connection with the third check method. For example, if themotion vectors VC1 to VC9 keep pointing in the same direction (e.g.,leftward) for a predetermined period or longer, the panned or tiltedstate is recognized; otherwise, the hand-shake or stationary state isrecognized.

For example, an additional condition that “the image shooting apparatus1 is not being panned or tilted” may be combined with the secondtriggering condition described above. Specifically, in that case, if“the width of variation of the position of the focus lens 31 hasremained smaller than or equal to a predetermined threshold value for apredetermined period T2 or longer and in addition the image shootingapparatus 1 is not being panned or tilted”, then the procedure proceedsto step S12; otherwise, it proceeds to step S15. Incidentally, when afar landscape is being shot, even in the panned state, the focus tendsto be locked.

Modifications etc. to the First Embodiment

What triggering condition to adopt in step S11 may be chosen by theuser. For example, the user may be allowed to choose which of the firstto fifth triggering conditions described above to adopt in step S11. Thechoice is made, for example, through operation of the operated portion26.

Of the first to fifth check methods described above, any two may becombined together. For example, the first and second check methods maybe combined together. In that case, in step S11, whether or not thefirst and second triggering conditions are fulfilled is checked. If atleast one of the first and second triggering conditions is fulfilled,the procedure proceeds to step S12; only if neither is fulfilled, theprocedure proceeds to step S15. Alternatively, only if both of the firstand second triggering conditions are fulfilled, the procedure proceedsto step S12; otherwise, the procedure proceeds to step S15.

The example described above deals with a case where a header filecontains one movie thumbnail so that this one movie thumbnail isassociated with one movie. Alternatively, a header file may contain aplurality of movie thumbnails so that these movie thumbnails are allassociated with one movie. In that case, in step S14, the moviethumbnail existing in the header file is not replaced with the (latest)movie thumbnail generated in step S13, but the movie thumbnail generatedin step S13 is added to the header file.

In a case where a plurality of movie thumbnails are associated with onemovie, for example, when the cursor 72 shown in FIG. 5 is moved to thethumbnail image TN3, the different movie thumbnails are displayed oneafter another at predetermined time intervals in the area of thethumbnail image TN3.

In this connection, a movie thumbnail may itself be a movie (hereinaftercalled a thumbnail movie). Even a thumbnail sound may be generated basedon the audio signal corresponding to a shot movie so that, when athumbnail movie is displayed, its thumbnail sound is simultaneouslyplayed back from the loudspeaker 28. Even when a thumbnail image is astill image, a thumbnail sound may be outputted.

As described earlier, if the triggering condition is not fulfilled evenonce during shooting of a movie, the movie thumbnail generated in stepS5 (the first thumbnail image candidate) eventually becomes the moviethumbnail associated with the movie. This movie thumbnail is generatedbased on the sensed-image signal at the timing that the movie starts tobe shot (the video signal of the frame with which the movie starts to beshot or of the frame immediately before that).

What movie thumbnail to associate with a movie when the triggeringcondition is not fulfilled even once during its shooting is not limitedto the one just described above. In such a case, the movie thumbnail hassimply to be generated based on the sensed-image signal (of a frame) atprescribed timing; for example, it may be generated based on thesensed-image signal immediately before or after shooting of a movie, orthe sensed-image signal of one of the frames of a movie being shot.

As described earlier, the contents of the memory card 18 can be freelyread by an external personal computer or the like. The contents of thememory card 18 can be reproduced (displayed as images and outputted assounds) on the display portion 27 and from the loudspeaker 28 asdescribed above, but may also be reproduced with a personal computer orthe like provided with a display and a loudspeaker.

In this embodiment, the part that functions as a view angle changingportion includes the driver 34. The view angle changing portion may bethought of as including also the operation keys 26 c and/or the CPU 23shown in FIG. 1, or the zoom lens 30 shown in FIG. 2. An autofocuscontrol portion is realized mainly with the AF value detection portion42 shown in FIG. 3, the CPU 23 shown in FIG. 1, and the driver 34 shownin FIG. 2.

In this embodiment, the thumbnail generating apparatus is built mainlywith the thumbnail generation portion 45 (or the video signal processingportion 13 including it) and the CPU 23. The thumbnail generatingapparatus may be thought of as including, in addition, one or more ofthe following: the view angle changing portion, the autofocus controlportion, a motion detection portion (corresponding to the motiondetection portion 44 shown in FIG. 3), a face area detection portion(corresponding to the face area detection portion 46 shown in FIG. 3),and a sound input portion (corresponding to the microphone 14 shown inFIG. 1). In step S5 shown in FIGS. 7 and 13, the thumbnail generationportion 45 functions as a first generating portion.

The first embodiment described above may incorporate any of the featuresof the second embodiment described later. Specifically, in step S11shown in FIG. 7, whether or not “the shutter button 26 b (see FIG. 1)has been pressed to request shooting of a still image” may be checked asa check of whether or not a sixth triggering condition is fulfilled.Then, if the sixth triggering condition is fulfilled, the procedureproceeds to step S12; if not, it proceeds to step S15.

Second Embodiment

Next, a second embodiment of the invention will be described. FIG. 15 isan overall block diagram of an image shooting apparatus 101 according tothe second embodiment of the invention. The image shooting apparatus 101is similar to the image shooting apparatus 1 shown in FIG. 1. The imageshooting apparatus 101 differs from the image shooting apparatus 1 shownin FIG. 1 in that the video signal processing portion 13 shown in FIG. 1is replaced with a video signal processing portion 113; in otherrespects, the image shooting apparatus 101 is quite like the imageshooting apparatus 1. Accordingly, no overlapping description will berepeated, and the following description of the second embodiment iscentered around the video signal processing portion 113.

The video signal processing portion 113 functions equivalently with thevideo signal processing portion 13; that is, based on the output signalof (the sensed-image signal from) the AFE 12, the video signalprocessing portion 113 generates the video signals of shot images, andfeeds the video signals to the compression portion 16 and the imageoutput circuit 20. The description of the video signal processingportion given earlier in connection with the first embodiment applies tothe video signal processing portion 113. When any description of thefirst embodiment is applied to the second embodiment, the difference ofthe reference numerals 13 and 113 between those embodiments is to beignored. The terms used in the description of the first embodiment applyin the second embodiment unless inconsistent. The drawings referred toin the description of the first embodiment are referred to in thedescription of this embodiment wherever necessary.

FIG. 16 is an internal block diagram of the video signal processingportion 113. The video signal processing portion 113 includes amovie/still image processing portion 41 and a thumbnail generationportion 142.

The movie/still image processing portion 41 in the video signalprocessing portion 113 is the same as the one shown in FIG. 3. Althoughunillustrated in FIG. 16, the video signal processing portion 113 alsoincludes an AF value detection portion 42, an AE value detection portion43, a motion detection portion 44, etc. like those shown in FIG. 3.According to the AF evaluation value, the CPU 23 adjusts, via the driver34 shown in FIG. 2, the position of the focus lens 31 so that an opticalimage of the subject is focused on the image sensing surface (lightreceiving surface) of the image sensing device 33. Moreover, accordingto the AE evaluation value, the CPU 23 adjusts, via the driver 34 shownin FIG. 2, the aperture of the aperture stop 32 (and also, wherenecessary, the amplification factor of the amplifier circuit in the AFE12) in order to thereby control the amount of light received (thebrightness of the image).

When a still image is shot, under the control of the CPU 23, thethumbnail generation portion 142 shown in FIG. 16 generates a thumbnailimage of the still image based on the sensed-image signal at the timingthat it is shot. More specifically, what the thumbnail generationportion 142 generates here is a video signal representing the thumbnailimage, composed of a luminance signal Y and color difference signals Uand V. This thumbnail image is a reduced image of a single still image(still picture) that has been shot and recorded, reduced, for example,through thinning-out. A thumbnail image of a shot still image (the videosignal representing the thumbnail image) is, with associationestablished between them, compressed by the compression portion 16(e.g., in compliance with the JPEG standard) and recorded to the memorycard 18. A thumbnail image associated with a shot still image is calleda still-image thumbnail.

On the other hand, when a movie is shot, under the control of the CPU23, the thumbnail generation portion 142 generates a thumbnail image ofthe movie based on the sensed-image signal at predetermined timing. Morespecifically, what the thumbnail generation portion 142 generates hereis a video signal representing the thumbnail image, composed of aluminance signal Y and color difference signals U and V. At what timingthis is done will be described in detail later. A thumbnail image of ashot movie is, with association established between them, compressed bythe compression portion 16 (e.g., in compliance with the JPEG standard)and recorded to the memory card 18. A thumbnail image generated to berecorded in association with a shot movie is called a movie thumbnail.The size of a movie thumbnail is, through thinning-out or the like,reduced to be smaller than the size of the images constituting the movie(or smaller than the size of still images). This reduction of imagesize, however, is not essential.

In the thumbnail image display mode, movie thumbnails and still-imagethumbnails stored in the memory card 18 are decompressed by thedecompression portion 19 and then converted by the image output circuit20 so as to be displayed on the display portion 27.

FIG. 5 shows an example of the screen displayed on the display portion27 in the thumbnail image display mode. In FIG. 5, the display area onthe display portion 27 is divided into four parts, with thumbnail imagesTN1, TN2, TN3, and TN4 displayed in the upper left, upper right, lowerleft, and lower right parts of the display area respectively. If morethumbnail images are stored in the memory card 18, operating theoperation keys 26 c in a predetermined way makes them appear on thescreen. The thumbnail images TN2 and TN3 bear a mark 71 indicating thatthey are movie thumbnails. Thus, the thumbnail images TN2 and TN3 aremovie thumbnails, while the thumbnail images TN1 and TN4 are still-imagethumbnails.

As shown in FIG. 5, a cursor 72 appears on the screen. The cursor 72moves across the screen as the operation keys 26 c are operated. FIG. 5shows a state in which the thumbnail image TN3 is being selected by thecursor 72. The number, such as “001”, appearing in a lower right part ofeach thumbnail image is its file number.

When a thumbnail image is being selected by the cursor 72, operating thekeys in a predetermined way causes the movie or still image associatedwith that thumbnail image to be read from the memory card 18. The movieor still image is then displayed over the entire screen on the displayportion 27. For example, when the keys are so operated as to start theplayback of the movie corresponding to the thumbnail image TN3, thescreen on the display portion 27 changes from FIG. 5 to FIG. 6, and themovie corresponding to the thumbnail image TN3 is played back over theentire screen on the display portion 27. In this state, when the keysare so operated as to stop the playback, the screen returns to FIG. 5.

Now, how a movie thumbnail is generated will be described. Presentedbelow are three examples of methods for generating a movie thumbnail.Unless otherwise stated, the following description of this embodimentfocuses on a given single movie.

First Generation Method

First, a first generation method will be described. FIG. 17 is a flowchart showing the procedure for generating a movie thumbnail accordingto the first generation method. The first generation method assumes thatonly one still image is shot during shooting of a movie.

First, in step S101, the CPU 23 checks whether or not the record button26 a has been pressed in the shooting mode. If not, the procedurerepeats step S101; if so, the procedure proceeds to step S102 (“Yes” instep S101).

In step S102, signal processing for a movie is started (recording isstarted). Specifically, after the procedure has proceeded to step S102,until it proceeds to step S107 when the record button 26 a is pressedagain, under the CPU 23, the video signal representing the shot imagesof a series of frames (i.e., a movie) is, along with the correspondingaudio signal, recorded sequentially via the compression portion 16 tothe memory card 18.

After step S102, the procedure proceeds to step S103. In step S103, theCPU 23 checks whether or not the record button 26 a has been pressedagain, that is, whether or not an instruction to stop recording has beenentered. If so, (“Yes” in step S103), the procedure proceeds to stepS107; if not, (“No” in step S103), it proceeds to step S104.

In step S104, the CPU 23 checks whether or not the shutter button 26 bhas been pressed to enter an instruction to shoot a still image. If not(“No” in step S104), the procedure returns to step S103; if so (“Yes” instep S104), it proceeds to step S105.

In step S105, concurrently with the signal processing for the movie,signal processing for a still image is performed. Specifically,concurrently with the signal processing for the movie, under the controlof the CPU 23, the movie/still image processing portion 41 generates avideo signal representing a still image from the sensed-image signal ofthe current frame (hereinafter called the still-image frame). Then, instep S106, the thumbnail generation portion 142 generates a moviethumbnail from the sensed-image signal of the still-image frame. Thus,the movie thumbnail is a reduced (or original-size) image of the stillimage shot.

Steps S105 and S106 are executed concurrently. The video signalgenerated in step S105 and representing the still image is recorded viathe compression portion 16 to the memory card 18. The video signalgenerated in step S106 and representing the movie thumbnail istemporarily recorded to the SDRAM 17. After step S106, the procedurereturns to step S103.

In step S107, to which the procedure proceeds from the step S103 when aninstruction to stop recording is entered, the signal processing for themovie is ended (recording is ended). That is, the recording to thememory card 18 of the video signal representing the shot images of aseries of frames along with the corresponding audio signal, which hasbeen performed since step S102, is stopped. Subsequently, in step S108,the movie thumbnail (the video signal representing the movie thumbnail)generated in step S106 is, with its association with the shot movieestablished, recorded to the memory card 18. On completion of step S108,the procedure shown in FIG. 17 ends.

During movie shooting, the user shoots a still image to record thesubject in a special state. A still image shot during movie shooting istherefore thought of as an image with a special significance to theuser. With the generation method under discussion, an imagecorresponding to a still image shot simultaneously while a movie isbeing shot is associated, as a movie thumbnail, with the movie, and thisallows the movie thumbnail to be an image aptly representing the movieor an image impressive to the user. This facilitates retrieval of thedesired movie, adding to the user's convenience. Moreover, to shoot astill image, the user has necessarily to operate the shutter button 26b. Thus, no extra operation or other burden is imposed on the user toselect a movie thumbnail.

The example just presented deals with a typical case where a moviethumbnail is generated from the sensed-image signal of the still-imageframe. Instead, a movie thumbnail may be generated from the sensed-imagesignal k frames before or after the still-image frame (where k is aprescribed natural number in the range from, e.g., one to several tens).In that case, the movie thumbnail generated in step S106 is a reduced(or original-size) image of the image shot k frames before or after thestill image is shot. This applies also to the second and thirdgeneration methods described later. Even when the image from which amovie thumbnail is generated is not quite the same as the shot stillimage, it is possible to obtain the same effect as described above.

With the first generation method, and also with the second and thirdgeneration methods described later, if the shutter button 26 b is notpressed even once during movie shooting, a reduced (or original-size)image of the image shot at prescribed timing is, as a movie thumbnailassociated with the shot movie, recorded to the memory card 18. Forexample, a movie thumbnail is generated based on the image of the frameimmediately before or after movie shooting, the image at the start orend of the movie, or the image of the frame a predetermined period afterthe start of movie shooting.

On the other hand, a still-image thumbnail is generated, for example, instep S106. The still-image thumbnail is then, in association with thestill image generated in step S105, recorded via the compression portion16 to the memory card 18. Typically, the movie thumbnail and thestill-image thumbnail generated in step S106 are the same.

Second Generation Method

Next, a second generation method will be described. FIG. 18 is a flowchart showing the procedure for generating a movie thumbnail accordingto the second generation method.

The procedure according to the second generation method includes stepsS101 to S107 and S110 to S112. The operations performed in steps S101 toS107 here is the same as those performed in the steps with the same stepnumbers in the first generation method (see FIG. 17), and therefore nooverlapping description will be repeated.

The second generation method assumes that a plurality of still imagesare shot during shooting of a movie. To make the description specific,the following description deals mainly with a case where two stillimages are shot during movie shooting.

During movie shooting, when the shutter button 26 b is pressed for thefirst time, then, in step S105, the video signal representing a firststill image is generated, and the video signal is recorded to the memorycard 18. Concurrently, in step S106, a first movie thumbnail isgenerated from the sensed-image signal of the frame (hereinafter calledthe first still-image frame) at which the first still image was shot.

Thereafter, while the movie continues to be shot, when the shutterbutton 26 b is pressed for the second time, then, in step S105, thevideo signal representing a second still image is generated, and thevideo signal is recorded to the memory card 18. Concurrently, in stepS106, a second movie thumbnail is generated from the sensed-image signalof the frame (hereinafter called the second still-image frame) at whichthe second still image was shot.

The first and second still-image frames are different, and the first andsecond movie thumbnails are different. The video signals representingthe first and second movie thumbnails are temporarily recorded to theSDRAM 17. Likewise, in a case where n still images are shot during movieshooting, n movie thumbnails are generated (where n is an integer of 3or greater).

In step S107, to which the procedure proceeds from the step S103 when aninstruction to stop recording is entered, the signal processing for themovie is ended (recording is ended). In the second generation method,after step S107, the procedure proceeds to step S110. In step S110,whether or not a plurality of still images have been shot during movieshooting is checked. If only one still image has been shot during movieshooting (“No” in step S111), the procedure proceeds to step S112, wherethe same operation as that performed in step S108 in the firstgeneration method is performed. Specifically, the movie thumbnail (thevideo signal representing the movie thumbnail) generated in step S106is, with its association with the shot movie established, recorded tothe memory card 18.

By contrast, if a plurality of still images have been shot as describedabove (“Yes” in step S110), the procedure proceeds from step S110 tostep S111. In step S111, according to a predetermined rule, one of aplurality of movie thumbnails generated is selected. After the selectionin step S111, the procedure proceeds to step S112, where the moviethumbnail (the video signal representing it) so selected in step S111is, in association with the shot movie, recorded to the memory card 18.On completion of step S112, the procedure shown in FIG. 18 ends.

Four examples of methods for achieving the selection in step S111 willnow be described one by one. The still image corresponding to the moviethumbnail selected in step S111 will be called the adopted still image.When the first still image mentioned above is the adopted still image,then, in step S111, the first movie thumbnail is selected to beassociated with the movie. Actually, in step S111, the adopted stillimage is selected. This automatically decides which movie thumbnail toselect in step S111.

As will be clear from the foregoing, the movie thumbnail selected instep S111 is generated based on the sensed-image signal at predeterminedtiming (of the still-image frame itself or a frame before or after it)relative to the timing (of the still-image frame) at which the adoptedstill image is shot.

The adopted still image is selected by a selection portion, which isrealized mainly with the CPU 23 and the video signal processing portion113.

First Selection Method: First, a first selection method will bedescribed. In the first selection method, which one of a plurality ofshot still images to select as the adopted still image is prescribed.

For example, the first or last one of the still images shot duringshooting of a movie is selected as the adopted still image. For example,suppose that, during movie shooting, a first, a second, . . . , and ann-th (where n is an integer of 3 or greater) are shot in this order;then the first or n-th still image is selected as the adopted stillimage. Needless to say, any of the second to (n−1)th still image mayinstead be selected as the adopted still image.

Second Selection Method: Next, a second selection method will bedescribed. In the second selection method, the degree of contrast of theimage is referred to.

In FIG. 19, the entire area of the image obtained from a one-frame-worthsensed-image signal is indicated by 175, and a part of that area isindicated by 176. The part 176 is called a contrast detection area. Thecontrast detection area 176 is defined, for example, near the center ofthe entire area 175. In FIG. 19, the contrast detection area 176 is asingle rectangular area; instead, it may is composed of a plurality ofareas defined inside the entire area 175, or may be as large as theentire area 175 itself. The entire area 175 may be thought of as theentire image-sensing area of the image sensing device 33 shown in FIG.2.

The contrast detection area 176 is defined for each of the still imagesshot during movie shooting. In a case where the second selection methodis adopted, a contrast detection portion 150 as shown in FIG. 20 isused. The contrast detection portion 150 is provided within the videosignal processing portion 113 shown in FIG. 15. The contrast detectionportion 150 includes an extraction portion 151, a HPF (high-pass filter)152, and a totaling portion 153.

The extraction portion 151 is fed with, as a signal representing a shotstill image, the video signal generated by the movie/still imageprocessing portion 41 or the sensed-image signal from the AFE 12. Fromthis video signal or sensed-image signal, the extraction portion 151extracts the luminance signal; here, it extracts only the luminancesignal from within the contrast detection area 176. The HPF 152extracts, from the luminance signal extracted by the extraction portion151, only a predetermined high-frequency component. As is well known,the high-frequency component extracted here increases roughly inproportion to the degree of contrast within the contrast detection area176 in the image.

The totaling portion 153 totalizes the high-frequency componentextracted by the HPF 152 and thereby calculates a contrast evaluationvalue commensurate with the degree of contrast within the contrastdetection area 176 in the image. The contrast evaluation value iscalculated for each shot still image, and is fed to the CPU 23. Thecontrast evaluation value increases as the degree of contrast increases.

The CPU 23 compares the contrast evaluation values calculated fordifferent still images; it then selects, as the adopted still image, thestill image corresponding to the greatest contrast evaluation value,that is, the still image with the highest degree of contrast within thecontrast detection area 176 in it, and accordingly decides which moviethumbnail to select in step S11.

When shooting is performed with a composition where the sky or the likeoccupies the background, the degree of contrast is usually higher if thesubject, such as a person, is arranged to appear large than if it isarranged to appear small. Generally, an image shot with the formersubject arrangement is more impressive to the user. Thus, adopting thesecond selection method helps obtain movie thumbnails that aptlyrepresent movies or are impressive to the user. This facilitatesretrieval of the desired movie, adding to the user's convenience.

Third Selection Method: Next, a third selection method will bedescribed. The third selection method employs area division based onbrightness information or color information.

In FIG. 21, the entire area of the image obtained from a one-frame-worthsensed-image signal is indicated by 175, and a part of that area isindicated by 177. The part 177 is called a detection area. The detectionarea 177 is defined, for example, near the center of the entire area175. The entire area 175 may be thought of as the entire image-sensingarea of the image sensing device 33 shown in FIG. 2.

The detection area 177 is defined for each of the still images shotduring movie shooting. Now, the procedure of the third selection methodwill be described with reference to the flow chart in FIG. 22.

First, attention is paid to one of a plurality of shot still images. Instep S151, based on the sensed-image signal of the still-image frame,the detection area 177 is divided into a plurality of brightness regionsor a plurality of color regions.

The following description deals with a case where the detection area 177is divided into a plurality of brightness regions. The brightness indifferent parts of the detection area 177 is identified based on thesensed-image signal from the pixels corresponding to the detection area177. For each pixel, the luminance signal takes a value, for example, inthe range from 0 to 255, which are here classified into a plurality ofranks, for example into nine brightness classes each covering 30consecutive values. As shown in FIG. 23, pixels for which the value ofthe luminance signal is 0 to 30 are classified into brightness class 1;pixels for which the value of the luminance signal is 31 to 60 areclassified into brightness class 2; . . . ; pixels for which the valueof the luminance signal is 211 to 240 are classified into brightnessclass 8; and pixels for which the value of the luminance signal is 241to 255 are classified into brightness class 9.

In a case where different luminance signal values are classified intonine brightness classes, the detection area 177 can be divided into ninebrightness regions, namely a first, a second, . . . , and a ninthbrightness region. The first, second, . . . , and ninth brightnessregions are composed of pixels classified into brightness classes 1, 2,. . . , and 9 respectively. Thus, one brightness region is composed ofpixels having similar brightness information. Depending on thesensed-image signal, the detection area 177 is divided into less thannine brightness regions; for example, when the image being shot isuniformly bright, the entire detection area 177 is occupied by a singlebrightness region.

After step S151, in step S152, the number of pixels forming eachbrightness region is counted to identify the largest brightness region(the one having the largest area, hereinafter called the largest dividedarea A). How large a brightness region is (its area) is proportional tothe number of pixels forming it.

Steps S151 and S152 are executed for each shot still image, so that thelargest divided area A is identified for each still image. In step S153,whether or not steps S151 and S152 have been executed for all stillimages is checked. When steps S151 and S152 have been executed for allstill images, the procedure proceeds to step S154. In step S154, forexample, the CPU 23 compares the largest divided areas A with oneanother. Then, according to the result of the comparison, the stillimage corresponding to, among all the largest divided areas A, the onewith the largest area is selected as the adopted still image.

For example, if the largest divided area A for a first still image hasan area of 10 pixels, and that for a second has an area of 15 pixels,then the second still image is selected as the adopted still image.

With similar operations, a case where the detection area 177 is dividedinto a plurality of color regions can be dealt with. Now, a descriptionwill be given of a case where the detection area 177 is divided into aplurality of color regions.

The color (hue) in different parts of the detection area 177 isidentified based on the sensed-image signal from the pixelscorresponding to the detection area 177. Based on this sensed-imagesignal, the color of each pixel is classified into one of a plurality ofcolor classes, for example nine color classes, namely a first to a ninthcolor class.

In a case where the color of each pixel is classified into one of ninecolor classes, the detection area 177 is classified into nine colorregions, namely a first, a second, . . . , and a ninth color region. Thefirst, second, . . . , and ninth color regions are composed of pixelsclassified into color classes 1, 2, . . . , and 9 respectively. Thus,one color region is composed of pixels having similar color information.Depending on the sensed-image signal, the detection area 177 is dividedinto less than nine color regions; for example, when the image beingshot is uniformly colored, the entire detection area 177 is occupied bya single color region.

In step S152, the number of pixels forming each color region is countedto identify the largest color region (the one having the largest area,hereinafter called the largest divided area B). How large a color regionis (its area) is proportional to the number of pixels forming it.

Steps S151 and S152 are executed for each shot still image, so that thelargest divided area B is identified for each still image. In stepS1153, whether or not steps S151 and S152 have been executed for allstill images is checked. When steps S151 and S152 have been executed forall still images, the procedure proceeds to step S154. In step S154, forexample, the CPU 23 compares the largest divided areas B with oneanother. Then, according to the result of the comparison, the stillimage corresponding to, among all the largest divided areas B, the onewith the largest area is selected as the adopted still image.

For example, compare a composition in which a green subject 178 isarranged to appear comparatively small in a white background as shown inFIG. 24A and a composition in which a green subject 178 is arranged toappear comparatively large in a white background as shown in FIG. 24B.In this case, the latter composition, in which the subject 178 appearslarger, yields largest divided regions A and B with larger areas.

The user tends to shoot an image so that the subject occupies a largearea on it, and an image so shot tends to be impressive to the user.Accordingly, adopting the third selection method helps obtain moviethumbnails that aptly represent movies or are impressive to the user.This facilitates retrieval of the desired movie, adding to the user'sconvenience.

The operation in step S151 (area division portion) is realized mainly bythe CPU 23 or the video signal processing portion 113.

Fourth Selection Method: Next, a fourth selection method will bedescribed. The fourth selection method pays attention to the intensityof the sound collected by the microphone 14 during shooting of a movie.

The audio signal processing portion 15 is capable of detecting theintensity or loudness of the sound, or of its frequency component in apredetermined band, collected by the microphone 14 during movieshooting. Based on the intensity or loudness of the sound, or of itsfrequency component in a predetermined band, the audio signal processingportion 15 calculates a sound intensity value for each shot still image.The following description deals with a case where the sound intensityvalue is commensurate with the intensity of sound, or of its frequencycomponent in a predetermined band. In a case where the sound intensityvalue is commensurate with the loudness of sound, or of its frequencycomponent in a predetermined band, the term “intensity” used inconnection with sound in the following description is to be read as“loudness”. Incidentally, the sound intensity value in this embodimentis to be understood as different from sound intensity value in the firstembodiment.

The sound intensity value corresponding to a still image is the averagevalue or peak value (maximum value) of the intensity of sound, or of itsfrequency component in a predetermined band, throughout the soundevaluation period corresponding to the still image. The sound evaluationperiod includes the period of the still-image frame; it may be theperiod of the still-image frame itself, or the period of a predeterminednumber of frames centered around the still-image frame.

The sound intensity value increases as the intensity of sound increases.The above-mentioned frequency component in a predetermined band is, forexample, that in the frequency band of human voice or in the audiblefrequency band. To extract a frequency component in such a predeterminedband from the audio signal fed from the microphone 14, the audio signalprocessing portion 15 uses a band-pass filter or the like.

The CPU 23 compares the sound intensity values calculated one for eachof the still images shot during movie shooting, and selects, as theadopted still image, the still image corresponding to the greatest soundintensity value.

When a movie is being shot on the occasion of a concert or party, acondition where the intensity of sounds is high is supposed tocorrespond to a condition where the atmosphere is livened up. Thus, astill image corresponding to a great sound intensity value is supposedto be impressive to the user. Accordingly, adopting the fourth selectionmethod helps obtain movie thumbnails that aptly represent movies or areimpressive to the user. This facilitates retrieval of the desired movie,adding to the user's convenience.

Third Generation Method

Next, a third generation method will be described. FIG. 25 is a flowchart showing the procedure for generating a movie thumbnail accordingto the third generation method.

The procedure according to the third generation method includes stepsS101 to S107, S110, S121, and S122. The operations performed in stepsS101 to S107 here is the same as those performed in the steps with thesame step numbers in the first generation method (see FIG. 17), and theoperation performed in step S110 is the same as that performed in thestep with the same step number in the second generation method (see FIG.18); therefore, no overlapping description will be repeated.

Like the second generation method, the third generation method assumesthat a plurality of still images are shot during shooting of a movie.

The description of the second generation method has dealt with a casewhere first a first still image is shot at a first still-image frame andthen a second still image is shot at a second still-image frame. Thefollowing description of the third generation method also assumes that afirst and a second still image are shot in that way, and in additionassumes that, after the shooting of the second still image, a thirdstill image is shot at a third still-image frame and further thereaftera fourth still image is shot at a fourth still-image frame.

In step S106, from the sensed-image signals of the first, second, third,and fourth still-image frames, a first, a second, a third, and a fourthmovie thumbnail are generated. In this generation method, the moviethumbnails generated in step S106 are each a part of the movie thumbnailto be associated with a single movie. Accordingly, in this generationmethod, the first, second, third, and fourth movie thumbnails generatedin steps S106 are called a first, a second, a third, and a fourththumbnail element image.

As in the second generation method, in the third generation method,after step S107, the procedure proceeds to step S110. In step S110,whether or not a plurality of still images have been shot during movieshooting is checked. If only one still image has been shot during movieshooting (“No” in step S110), the procedure proceeds to step S122, wherethe same operation as that performed in step S108 in the firstgeneration method is performed.

By contrast, if a plurality of still images have been shot as describedabove (“Yes” in step S110), the procedure proceeds from step S110 tostep S121. In step S121, the four thumbnail element images generated instep S106 are synthesized together to generate a definitive moviethumbnail. After the synthesis in step S121, the procedure proceeds tostep S122, where the movie thumbnail (the video signal representing it)resulting from the synthesis in step S121 is, in association with theshot movie, recorded to the memory card 18. On completion of step S122,the procedure shown in FIG. 25 ends.

Now, two examples of methods for the synthesis in step S121 will bedescribed. In the generation method under discussion, the first tofourth still images are all adopted still images.

First Synthesis Method: First, a first synthesis method will bedescribed. In FIG. 26, the movie thumbnail resulting from synthesisaccording to the first synthesis method is indicated by 180, and thefirst, second, third, and fourth thumbnail element image are indicatedby 181, 182, 183, and 184 respectively. The size of the movie thumbnail180 is, for example, the same as that of the thumbnail TN3 shown in FIG.5. Thus, when the movie thumbnail 180 is created, the size of theindividual thumbnail element images are appropriately reduced, forexample, through thinning-out.

In a case where the first synthesis method is adopted, in the thumbnailimage display mode, the movie thumbnail 180 is displayed, for example,in the position where the thumbnail TN3 is displayed.

In a case where five or more still images have been shot, four of themare selected as adopted still images, and a total of four thumbnailelement images corresponding to them are synthesized together togenerate a movie thumbnail. For example, the first four or last fourstill images are selected as adopted still images.

Second Synthesis Method: Next, a second synthesis method will bedescribed. In a case where the second synthesis method is adopted, themovie thumbnail resulting from the synthesis in step S121 is composed ofa plurality of images each the same size as the thumbnail TN3 shown inFIG. 5. In a case where a first to a fourth still image have been shot,the movie thumbnail resulting from the synthesis is composed of a firstto a fourth thumbnail element image each the same size as the thumbnailTN3.

In a case where, during shooting of the movie corresponding to thethumbnail TN3, a first to a fourth still image are shot, when thethumbnail image display mode is selected, first, a first thumbnailelement image is displayed in the position of the thumbnail TN3. Apredetermined period (e.g., one second) thereafter, a second thumbnailelement image is displayed in the position of the thumbnail TN3 in anupdating fashion. Likewise, every time a predetermined period passes,the image displayed in the position of the thumbnail TN3 is updated witha third, and then a fourth thumbnail element image, and then the firstthumbnail element again.

The above updating of the display may be performed only when the cursor72 is at the thumbnail TN3, or irrespective of where the cursor 72currently is.

Modifications etc. to the Second Embodiment

In the second embodiment, any feature of any one of the differentgeneration methods (first to third generation methods) described abovemay be applied to any other of them unless inconsistent.

There is no restriction on the timing at which a movie thumbnail isactually generated. A movie thumbnail may be generated on receipt of asensed-image signal from the AFE 12 during movie shooting. An imagebased on which to generate a movie thumbnail afterwards may be selectedduring movie shooting so that, based on that image, a movie thumbnail isgenerated later (e.g., when it is displayed on the display portion 27).Anyway, the sensed-image signal from which a given movie thumbnail isgenerated is the same.

As described earlier, the contents of the memory card 18 can be freelyread by an external personal computer or the like. The contents of thememory card 18 can be reproduced (displayed as images and outputted assounds) on the display portion 27 and from the loudspeaker 28 asdescribed above, but may also be reproduced with a personal computer orthe like provided with a display and a loudspeaker.

In the second embodiment, the thumbnail generating apparatus is builtmainly with the thumbnail generation portion 142. The thumbnailgenerating apparatus may be thought of as including the CPU 23.

A movie thumbnail may itself be a movie (hereinafter called a thumbnailmovie). Even a thumbnail sound may be generated based on the audiosignal corresponding to a shot movie so that, when a thumbnail movie isdisplayed, its thumbnail sound is simultaneously played back from theloudspeaker 28. Even when a thumbnail image is a still image, athumbnail sound may be outputted.

1. A thumbnail generating apparatus that, based on a sensed-image signalrepresenting a subject received from an image shooting portion providedin an image shooting apparatus capable of shooting a movie, generates athumbnail image associated with the shot movie, that includes a firstgeneration portion generating, based on the sensed-image signal atprescribed timing, a first candidate thumbnail image as a candidate forthe thumbnail image, and that, when a predetermined triggering conditionis fulfilled during shooting of the movie, based on the sensed-imagesignal at predetermined timing relative to when the triggering conditionis fulfilled, generates a second candidate thumbnail image differentfrom the first candidate thumbnail image and associates, as thethumbnail image, the second candidate thumbnail image with the movie. 2.The thumbnail generating apparatus according to claim 1, wherein theimage shooting apparatus includes a view angle changing portion thatallows an angle of view at which the image shooting portion performsshooting to be changed, and the triggering condition includes acondition that, after zooming-in is performed to decrease the angle ofview, no change has been made in the angle of view by the view anglechanging portion for a predetermined period or longer.
 3. The thumbnailgenerating apparatus according to claim 1, wherein the image shootingapparatus includes an autofocus control portion that automaticallyadjusts a position of a focus lens so that an optical image representingthe subject is focused on an image sensing surface of an image sensingdevice provided in the image shooting portion, and the triggeringcondition includes a condition that a width of variation of the positionhas remained smaller than or equal to a predetermined threshold valuefor a predetermined period or longer.
 4. The thumbnail generatingapparatus according to claim 1, wherein the image shooting apparatusincludes a motion detecting portion that detects motion within a motiondetection area in an image based on the sensed-image signal, the motiondetection area being defined in a shot image included in the movie, andthe triggering condition includes a condition that a magnitude of thedetected motion has remained smaller than or equal to a predeterminedthreshold value for a predetermined period or longer.
 5. The thumbnailgenerating apparatus according to claim 1, wherein the image shootingapparatus includes a face area detection portion that detects a person'sface area in a shot image included in the movie based on thesensed-image signal, and the triggering condition includes a conditionthat a size of the detected face area is larger than or equal to apredetermined threshold value.
 6. The thumbnail generating apparatusaccording to claim 1, wherein the image shooting apparatus includes asound input portion that receives input of sound from outside, whetheror not the triggering condition is fulfilled is checked based onintensity or loudness of the sound inputted during shooting of themovie, and the second candidate thumbnail image is generated from thesensed-image signal at predetermined timing relative to when theintensity or loudness of the sound, or the intensity or loudness of afrequency component of the sound in a predetermined band, is maximalduring shooting of the movie.
 7. The thumbnail generating apparatusaccording to claim 1, wherein when the triggering condition is fulfilledduring shooting of the movie, the second candidate thumbnail image isgenerated from the sensed-image signal at a frame during which thetriggering condition is fulfilled or at a frame close to that frame. 8.The thumbnail generating apparatus according to claim 1, wherein whenthe triggering condition is not fulfilled even once during shooting ofthe movie, the first candidate thumbnail image is associated, as thethumbnail image, with the movie.
 9. The thumbnail generating apparatusaccording to claim 1, wherein the image shooting apparatus is capable ofshooting a still image during shooting of the movie, and the triggeringcondition includes a condition that an instruction to shoot the stillimage is entered.
 10. An image shooting apparatus capable of shooting amovie, comprising: the image shooting portion and the thumbnailgenerating apparatus according to claim
 1. 11. A thumbnail generatingapparatus that, based on a sensed-image signal representing a subjectreceived from an image shooting portion provided in an image shootingapparatus capable of shooting a still image during shooting of a movie,generates a thumbnail image associated with the shot movie, and that,when a still image is shot during shooting of the movie, generates thethumbnail image from the sensed-image signal at predetermined timingrelative to when the still image is shot.
 12. The thumbnail generatingapparatus according to claim 11, wherein the thumbnail image isgenerated from the sensed-image signal representing the still image. 13.The thumbnail generating apparatus according to claim 11, wherein thethumbnail generating apparatus includes a selection portion that, when aplurality of still images are shot during shooting of the movie, selectsone of the still images as an adopted still image, and the thumbnailimage is generated from the sensed-image signal at predetermined timingrelative to when the adopted still image is shot.
 14. The thumbnailgenerating apparatus according to claim 13, wherein which of the stillimages to select as the adopted still image is prescribed.
 15. Thethumbnail generating apparatus according to claim 13, wherein thethumbnail generating apparatus includes a contrast detection portionthat defines a predetermined contrast detection area in each of thestill images and that, based on the sensed-image signal representing theshot still images, detects a degree of contrast within the contrastdetection area for each of the still images, and the selection portionselects the adopted still image based on results of comparison of thedegree of contrast among the still images.
 16. The thumbnail generatingapparatus according to claim 13, wherein the thumbnail generatingapparatus includes an area division portion that defines a predetermineddetection area in each of the still images and that, based on thesensed-image signal representing the shot still images, divides, in eachof the still images, the detection area into a plurality of brightnessregions or a plurality of color regions, and the selection portionidentifies, in each of the still images, a brightness region or colorregion having a largest area among all the brightness regions or colorregions, and selects the adopted still image based on results ofcomparison of an area of the brightness region or color region havingthe largest area among the still images.
 17. The thumbnail generatingapparatus according to claim 13, wherein the image shooting apparatusincludes a sound input portion that receives input of sound fromoutside, the thumbnail generating apparatus includes a sound detectionportion that detects, for each of the shot still images, intensity orloudness of the sound, or intensity or loudness of a frequency componentof the sound in a predetermined band, corresponding to timing that thestill image is shot, and the selection portion selects the adopted stillimage based on results of comparison of the intensity or loudness of thesound or the intensity or loudness of the frequency component of thesound in the predetermined band among the still images.
 18. Thethumbnail generating apparatus according to claim 11, wherein when aplurality of still images are shot during shooting of the movie, part orall of the still images are selected as adopted still images so thatthere are a plurality of adopted still images, for each of the adoptedstill images, a thumbnail element image is generated from thesensed-image signal at predetermined timing relative to when the adoptedstill image is shot, and the thumbnail image is generated bysynthesizing together thumbnail element images of the adopted stillimages.
 19. An image shooting apparatus capable of shooting a stillimage during shooting of a movie, comprising: the image shooting portionand the thumbnail generating apparatus according to claim 11.